The dates used when inputting information into a bookkeeping system such as Crunch, are very important. Having the wrong date has implications, such as the invoice or expense going into the wrong set of annual accounts. This would also affect the amount of Corporation Tax you pay.
Let your accountant know if you've either invoiced your client a large amount in advance, or if you've invoiced them for work you completed a while ago. Your accountant will need to alter your accounts because they need to make sure your profits match the correct period of time when the work was completed. If you need any help with this, ask to speak to an accountant and they can assist you with the whole process.
Here is an example where the accounting period ends 30 April 2017 - if you provided a client with consulting services between 1 April 2017 and 31 May, then afterwards invoiced the client £2,000 on 1 June. £1,000 of this invoice would be adjusted and moved into the 30 April 2017 accounts.
It could also impact when an amount is included on a VAT return for clients on flat rate scheme amongst others.
At Crunch VAT to HMRC is calculated when the invoice or expense is paid. Therefore it is important when recording a payment, the date entered will be when the money entered or left your bank account.