Paying Tax On Money Owed?

Hi There, I hope I'm posting in the relevant section. After being out of work for a couple of years due to health reasons, I'm hoping to get back to work this year, and I'm now chasing up a company I previously worked for who owe me money. I'm self employed - CIS - but I worked for this company continuously for around 5 yrs on a self employed basis. I would invoice/timesheet them weekly, and they would pay weekly. I would deduct the tax on my invoice and they would pay the tax. I've now completed the rest of my owed invoices and I'm ready to send them over to the company - along with the other invoices of mine they already have, and haven't paid. My question is, should I be seeking the full amount pre tax, or go about getting the money the way I usually would when I worked for them? So essentially they pay the tax their end once they receive my invoices. As this is money owed from a couple of years ago, I not sure how this works now. I hope this makes sense. Any help would be much appreciated, Thank you.

Hi BigA101,
You would submit the invoice in the same maner as you did previously. as it relates to previous years,
You will also need to submit tax returns for the years in question. years prior to 2020 are now out of date.
Thank you.