Invoices/wage slips without company letterhead

Assalam o Alaikum

I will apply for ILR next month, I have gone through the guidance notes.. I am registered as self employed, I worked for two or three different companies and after payment the invoices that they gave me were not on their letter head, although money that was transferred to my account shows their company name and all that.. will it be acceptable to Home office plus I have deposited quarterly NI that self employed ppl pay but I did that online, I don't have receipts for that, However my bank statement shows it.. will it be okay as well. Kindly guide

Regards

What the invoice explanations or payment summaries must show:

You must send summaries or explanations created by your managing agent (who is usually an accountant). These explanations should include a breakdown of the gross salary, tax deductions and dividend payments made to you. The total gross salary and dividend payments should be the same as your earnings. The payment summary should enable us to check that these correspond with the net payments into your personal bank account.