Invoice creation from billable time - calculation errors

I seem to have stumbled upon a rounding bug - When I create an Invoice from billable time, the amounts are different from what the entries in Billable Time report. These discrepancies range from 5 to 10 cents per item.

2h 55m billed at $15/h shows $43.75 on Billable Time, the Invoice reads $43.80 (2.92 x 15).

Is there a way to fix this without rounding the time values to 15 minute increments?

This discrepancy arises from different rounding rules being applied. Under Billable Time, the calculation is, for all intents, exact. But when the invoice is created, the amount is rounded to the number of decimal places used for the display. Then the calculation is performed.

@lubos, I definitely agree with @kosmro that the rounding and calculation protocol should be the same in both cases. Either could be justified, but why not use the more exact approach, with the invoice matching the billable time calculation?

Actually the issue here is that under Billable Time, you enter time in hours and minutes. (e.g. 1 hour 22 minutes)

But when invoice is generated, it is converted to decimal quantity rounded to two decimal places. This is purely to make it so invoice can show quantity in qty column.

For example, 1 hour 30 minutes will become 1.5 quantity. So far so good. But what if the time is 2 hour and 55 minutes? Then we end up with quantity 2.9166666666666… rounded to 2.92. This can cause difference between billable time and invoice.

From accounting point of view, this is not an issue. It’s baked into the system that you can charge different amount than what you’ve recorded in billable time and Manager will automatically make necessary write-ons or write-offs.

But I do agree, perhaps Billable Time should use the same calculation method as is used on invoices to avoid this inconsistency.

I agree it would be better if the calculation method is the same, @lubos. But I very much hope that would not mean we have to enter decimal times. That would be a nightmare, because who wants to figure that 2 hours and 55 minutes equates to 2.916666666666?

Obviously, Manager knows the more precise time number. It seems the question is whether to round the time first and repeat the calculation for the invoice, producing the write-ons and write-offs, or make the precise calculation and only round the time number for display. The first approach might appeal to customer auditors, as the invoice would appear consistent. The second is closer to the accounting truth. I would favor that. If a user encountered a customer who complained, he or she could add a note explaining that time is rounded for display purposes.

any update on the above rounding issue? also, I’d appreciate your feedback on:

  1. Is there a way to specify a Billable Time unit, i.e. hourly rate, daily rate etc?
  2. In reports, is there a way to generate a customer report detailing billable time?
  3. It would be great if we could perhaps create projects, maybe under customers, or billable time, and then specify hourly rate (or daily rate) then be able to report time spent vs. invoices paid … per project


I’ve got 2 projects with the same client, and I send weekly invoices detailing hours spent on projects (I specify the project name in “description” → billable time), then I add up time spent on each project manually and edit them in the invoice.

No, you must enter time in hours and minutes.

[quote=“JONGAR, post:5, topic:3746”]
is there a way to generate a customer report detailing billable time
[/quote]No. The Billable Time Report summarizes amounts in each customer’s account.

[quote=“JONGAR, post:5, topic:3746”]
I add up time spent on each project manually and edit them in the invoice.
[/quote]If I understand you correctly, you don’t need to do this. If you create the sales invoice from the Billable Time module (or Billable Expenses, for that matter), you have the option of ticking off the time/expense entries you want to include in the invoice. So you can create one invoice per project.

Thanks for all your fantastic support in advance :slight_smile: :smile:
I may be wrong, but from your comments I understand that: calculation errors ?always occur/are common when using ‘Billable Time’ to create invoices; these calculation errors are (then) resolved in the ‘Billable Time Transactions’ (or as ‘in progress/movement’) which should not affect the values of the totals/balances. ?is that somewhat correct.

  • I am trying to understand why the calculation errors occur, given that I only charge $40/hour (no tax is involved) and generally work in hourly (quarter, or half) - but may have documented 25minutes.
    In my case over the previous three months I have had a ‘write-on’ of $0.13, and ‘Write-offs’ of $16.67, $460 and $770.
    I believe it’s likely that most of these amounts reflect the number of uninvoiced work (or ‘in progress’)?
    As it was not immediately clear from my readings previous on this same topic, I would appreciate it if you could you outline how it would be possible for me to find out/see where/to which invoice the write-on/write-off apply/refer to so that I can investigate why they have occurred.
    Many, many thanks :smile:

Let’s clarify an important point. Nothing in this topic refers to errors except the title. The behavior reported has to do with rounding. The calculations themselves have always been correct.

Whatever time you record in the Billable Time module will be the basis for the sales invoice. If you want to bill in quarter-hour increments, you must enter your time accordingly.

If you want to see what has been invoiced, look at the Billable Time tab listing. Every entry has a status indicator.

I cannot make any guess about your reported “write-on” and “write-offs” because you did not provide any information. I will say some of the numbers you mentioned seem quite large for rounding errors. But I don’t know what you are comparing or what you expected. Can you furnish more details?

If there is uninvoiced work, it will show up in both assets and income categories. Depending on how you may have renamed automatic accounts, the asset account should be called something like Billable time and the income account should be something like Billable time - work in progress. Work that has not been invoiced will also be accessible from the Customers tab by drilling down in the appropriate column (which disappears if all work has been invoiced).

Thank you for your explanation. My reference to ‘calculation errors’ was not accurate, I think. If there were uninvoiced amounts (some hours that were to be invoiced at the end of the next month), would that prompt a ‘write-off’ to take place? Also, is it at all possible to identify where/which invoice is involved in the ‘write-on/off’’ in some way?
I will try to follow up with some further checking myself - a little later… it is almost 2:00am here in South Australia. I will reply with some additional details after I have done a little digging myself…
Thanks again… nemo51

When you are awake again, could you please clarify exactly what you mean by “write-on” and write-off?" I am struggling to interpret what you mean in the original context of this topic, which focused on rounding differences. You may, in fact, be talking about something completely different. Thanks.

Write-ons and write-offs in billable time will automatically happen if you bill client less or more than what was recorded in billable time.

I think it’s a good idea to make a report which could show how much was written-off or written-on per invoice.

Although it is not a calculation error, it is more ore less a presentation order.
Billable time of 1 hour is shown on the invoice as 1 and is centered in the column
1 hour and 30 minutes is shown as 1.5 and 1 hour and 15 minutes is shown as 1.25
It is possible to change the presentation standard to 0.00 This looks more professional.
Thanks in advance

Greetings all - I would like to know how to run a custom query/report to discover the adjustments that apply per invoice. (Unfortunately, I have not had time to search for directions on how to do so.) The reason being that I am still somewhat confused around the issue of ‘Billable Time’ and adjustments/‘Write-off’. I am attaching a couple of screenshots to display the apparently automatic ‘write-off’ adjustments that seem to be having an effect on the Summary ‘Billable Time not yet invoiced’ which appears to be quite a high value (although all but $250 has been invoiced and fully receipted. It appears that I am unable to edit the ‘Write-offs’ and am unsure how to rectify this. Any advice would be most appreciated - thanks gratefully :slight_smile:

Please don’t ask others how to do things when you haven’t looked for answers yet yourself. If you do the research and still have questions, please be specific about them so someone can help. [quote=“nemo51, post:13, topic:3746”]
I am attaching a couple of screenshots

All your screen shots are too low in resolution to read, the last two especially. And you have blanked out so much information it is impossible to determine whether they are in any way unusual. If you think something is wrong, explain what you think is wrong and how it was produced. Then someone can help.

This is not a standard account. Is it one you created or renamed? If so, which. You should understand the the entire billable time module will work only with the default accounts, although they can be renamed.

Finally, let me make the point that unless you do unusual things with billable time, such as editing entries to invoice more or less time than recorded, there should be no adjustments or automatic transactions at all.

How have you been invoicing the Billable Time, if done correctly the Billable Time should reduce and be transfer to Accounts Receivable when the invoice is created. Does you Billable Time account show any reduction figures. Unfortunately, due to the scaling I can’t read the screen shot details even after zooming.

Thanks all for your feedback. I sincerely apologise for the resolution - unfortunately, unless I reduce the size of the image before I do a screen capture, I am unable to get a full screenshot. The information that has been blanked are company names that do not reflect any Manager properties. Although I have tried to run a report within ‘billable time’ a ‘keyword’ is requested - without a dropdown list, the words I have tried (time, hours, $) these do not seem to match the requirements. I have run a report for all general ledger transactions since 01/07/15 which may have highlighted and account for a period when I transitioned from creating a manual invoice for my hours worked to using billable hours. I will follow up on this and all your advice. I will update again after cross checking the billable time and invoices issued (and receipted). Many thanks, very much appreciate your assistance.

Billable time adjustment is caused by some invoice which is billing less than the value of billable time attached to it. So Manager needs to make a write-off on that unbilled time portion.

Since the adjustment is on 04/01/2016, this entry was caused by sales invoice issued on this date.